Effect of plant materials on microbial transformation of amino sugars in three soil microcosms

Amino sugars, being predominantly of microbial origin, can help elucidate the role of microbes in carbon and nitrogen cycling in soils. However, little is known about the microbial degradation and synthesis of soil amino sugars as affected by plant-derived organic materials. We conducted a 30-week microcosm study using three soils amended with soybean leaf or maize stalk to investigate changes in the amounts and patterns of amino sugars over time. The total soil amino sugar content initially increased during the incubation, but later decreased. Amino sugar content of soil amended with maize stalk peaked at an earlier time than it did for soybean leaf, suggesting nutrient quantity and substrate composition influence microbial transformation. Temporal dynamics of the proportion of total soil amino sugar to organic matter after plant material addition conformed to parabolic models (r>0.8; p<0.01), which tended to converge over time. The models predicted that the proportions would ultimately approach the initial values as determined before amendment. These findings suggest that soil organic matter has the ability to maintain a baseline steady-state level of amino sugars, and support the interpretation of soil amino sugar reservoir as two components: the Stable Pool (SP) and the Transition Pool (TP).